Pushing the limits of 5.56

[AlaskaRed]

With the USSA range being open to 1000 yards my imagination has gone wild with possibilities. Right now I'm planning a test of 5.56, to see how can it can be pushed and still maintain it's accuracy and effectiveness. If there's any interest I'll post my plans and progress.

[slim]

Interested.

[AlaskaRed]

Here's the plan as it stands now, I'd like to get the reloading done this week and the Test Loads figured out by the weekend.

This rifle has a 20" RRA barrel in an HBAR contour with a .223 wylde chamber and a 1:8 twist. The optic I'll be using is a Vortex Viper PST 4-16 FFP in Mil/Mil. For this test I'll be firing off a harris bipod and a TAB rear bag.

The ammo

For this test I'll be sticking to magazine loaded ammo, this means 77gr SMK's loaded to 2.250 COAL. I'll be starting with Varget as a propellant since I have load data for that, but I'll also be testing RE15, BLC(2), and TAC in a search for higher velocities.

According to JBM to keep the 77gr SMK supersonic to 1000 yards I'll need a muzzle velocity of about 3350 fps. This simply isn't realistic to expect from a 5.56, my current load(which exceeds the max load in the manual by 0.1gr) gives me ~2625fps. Perhaps I can get up to 2750 from another powder, but 3350fps simply isn't feasible.
2750 isn't an arbitrary choice either, it's about what I'll need to keep the round supersonic to 800 yards. We'll be exploring what happens when the bullet goes subsonic.

Test loads must meet the criteria of 1 moa or less(verified at 300 yards) at the highest safe velocity for that particular powder.

Safe velocity is defined as a velocity at which no pressure signs are indicated. This includes flattened primers, primer cratering, injector smearing, ect...

The Test
This is a test to determine the effective range of 5.56, which means that the rifle must be accurate enough to consistently hit it's target and still have enough energy for adequate penetration. So the test will have two phases, one to test the limits of accuracy and a second to test terminal ballistics.

The Accuracy Test
Starting at 500 yards the Test Loads will be fired at an Appleseed fullsize KD target. Scoring at least 8 hits out of 10(in the 4 or 5 ring) indicates adequate accuracy and the target distance will be increased 100 yards until the round is no longer capable of meeting this threshold. The furthest range at which the round was able to meet the 8/10 criteria will be considered the maximum practical range for that test load.
Once the maximum practical range has been determined for all the test loads I will conduct a test of terminal ballistics.

Terminal Ballistics Test
Once the maximum practical range of a load is determined the terminal ballistics at that range will be tested. Using 10% Knox gelatin covered in a layer of denim, the round must penetrate at least 13" to be considered effective. If the round fails to penetrate 13" the test will be repeated. If it fails a second time the range will be reduced 100 yards and the test conducted again until adequate penetration is achieved.

[ItsanSKS]

I'll be looking forward to this test!  Hope I'll be able to help. 

[grunt soldier]

I'm looking forward to your results also.

[Camljr]

I recently checked the loading data on Accurate #2460 powder;
for a 77 Sierra HPBT MK, it pushes over 2,743 FPS with 21.6 grains at 2.26 col.
CUP is 54,400.

Maybe if you loaded slightly hotter with a longer overall length (loaded singly), you may reach closer to 3,000 FPS.

I will be interested to see the results.

Of course, like engines, where there is no substitute for more cubic inches,
with guns, there is no substitute for a larger caliber....

Here's the plan as it stands now, I'd like to get the reloading done this week and the Test Loads figured out by the weekend.

This rifle has a 20" RRA barrel in an HBAR contour with a .223 wylde chamber and a 1:8 twist. The optic I'll be using is a Vortex Viper PST 4-16 FFP in Mil/Mil. For this test I'll be firing off a harris bipod and a TAB rear bag.

The ammo

For this test I'll be sticking to magazine loaded ammo, this means 77gr SMK's loaded to 2.250 COAL. I'll be starting with Varget as a propellant since I have load data for that, but I'll also be testing RE15, BLC(2), and TAC in a search for higher velocities.

According to JBM to keep the 77gr SMK supersonic to 1000 yards I'll need a muzzle velocity of about 3350 fps. This simply isn't realistic to expect from a 5.56, my current load(which exceeds the max load in the manual by 0.1gr) gives me ~2625fps. Perhaps I can get up to 2750 from another powder, but 3350fps simply isn't feasible.
2750 isn't an arbitrary choice either, it's about what I'll need to keep the round supersonic to 800 yards. We'll be exploring what happens when the bullet goes subsonic.

Test loads must meet the criteria of 1 moa or less(verified at 300 yards) at the highest safe velocity for that particular powder.

Safe velocity is defined as a velocity at which no pressure signs are indicated. This includes flattened primers, primer cratering, injector smearing, ect...

The Test
This is a test to determine the effective range of 5.56, which means that the rifle must be accurate enough to consistently hit it's target and still have enough energy for adequate penetration. So the test will have two phases, one to test the limits of accuracy and a second to test terminal ballistics.

The Accuracy Test
Starting at 500 yards the Test Loads will be fired at an Appleseed fullsize KD target. Scoring at least 8 hits out of 10(in the 4 or 5 ring) indicates adequate accuracy and the target distance will be increased 100 yards until the round is no longer capable of meeting this threshold. The furthest range at which the round was able to meet the 8/10 criteria will be considered the maximum practical range for that test load.
Once the maximum practical range has been determined for all the test loads I will conduct a test of terminal ballistics.

Terminal Ballistics Test
Once the maximum practical range of a load is determined the terminal ballistics at that range will be tested. Using 10% Knox gelatin covered in a layer of denim, the round must penetrate at least 13" to be considered effective. If the round fails to penetrate 13" the test will be repeated. If it fails a second time the range will be reduced 100 yards and the test conducted again until adequate penetration is achieved.

[fisherdawg]

Man, I want to be there too!

[AlaskaRed]

I recently checked the loading data on Accurate #2460 powder;
for a 77 Sierra HPBT MK, it pushes over 2,743 FPS with 21.6 grains at 2.26 col.
CUP is 54,400.

Maybe if you loaded slightly hotter with a longer overall length (loaded singly), you may reach closer to 3,000 FPS.

I will be interested to see the results.

I want to use this first test to see the practical limit of the AR15, which means testing the ammo I can load in a magazine. When I'm done, I'll consider looking at other bullets like the 80gr SMK's that need to be single loaded.   

[gonejohnny]

I've seen guys have some (seriously amazing) success w/ Berger 82's loaded to mag-length over 24.5g of Varget through pretty much the same rifle you mention...
But...
One  shooter in particular switched out a season later... Said he couldn't get his success to replicate between different barrels... Some times you get a window of opportunity for a sweet spot... other times... things start acting finicky... sometimes out the gate.

Can't help you with your 77's at that distance... But I've experienced 80 SMK's in front of 24.5 of RE15 both jumped and jammed. They're almost as forgiving as that D-Target.

Sounds like a fun experiment! Wish you the best of luck and please post back with your notes!
- Johnny

[jmdavis]

80's single loaded will make it to 1000, but the problem will be that they are probably subsonic by 850 or 900. 90's were tested in the .223 AMU chamber and they made the trip and stayed supersonic. Groups were supposedly pretty good, but the truth is that it is easier to make other calibers perform better with less work. I would not load 80's or Berger 82's to mag length. I believe that you will need them seated and perhaps only .010 off the lands to make the trip and have any hope of not going subsonic.

Check the forums at

http://www.usrifleteams.com/


There are highpower and long range forums there.

[Aromatic]

No question that the 5.56 can be pushed to 1k but I have no interest in non mag length loads.  I would much prefer info about barrel length with mag length 77s or similar.

[Arrigetch]

Reasonably expect 800-850 yards effective max distance with 77gr (hits transonic boundary about 875 yds), your mileage may vary with barrel length, etc.  A major problem is bucking the wind at longer distances with 5.56.  I shoot at Lewistown, PA (1050 yds), and use at least 175gr .308 to consistently hit targets at 1000 yds.  It is fun to shoot long range 5.56 though too.

Great to hear that Alaska is now going to have a 1000 yd range.... I am hoping to finally move back!

[slim]

Whats the elevation at the range up there?

[fisherdawg]

Whats the elevation at the range up there?

Approx. 300' asl

[jmdavis]

It is possible to single load an AR with non mag length rounds and get off 10 shots in 70 seconds. If I were trying to shoot 1k, I would want those bullets out far enough to be at an accuracy node as far as oal went in relation to chamber length.

The reason that people single load for 1k (whether an AR-15 space gun or a tubegun or a palma gun) is that it lets them not be as limited in their oal and loads.

[Niskibum]

What is considered maintaining effectiveness? What bullets will be used and what is the lowest speed at which that bullet will expand? I have deer hunted with my AR, and understood that with the bullets I was using my max effective range was about 300 yards for an ethical kill. Are there any AR bullets that will expand sub-sonic?

[jmdavis]

Effectiveness is relative to the purpose. What is "effective" on a deer sized animal is overkill for a groundhog. An "effective" round in combat, may be more range limited in hunting. What works for punching paper at 600 or 700 yards may be worfully unstable at 1000.

At the first military Appleseed in 2009, boltgun71 used a  combination of Appleseed and Army Marksmanship Unit methods to train a group of Squad Designated Marksmen from a repurposed National Guard Battalion. In that 5 day course with 300 live rounds (including a 50 round Alt C military qualification). Those men showed effectiveness out to 700 meters with M4's and Acog's and had a 69% first round hit at that range. That is effective in the context of their mission.

I would not hesitate to shoot a groundhog and 500 or 600 yards with an Accurate scoped AR. I regularly shoot to 600 yards with irons. For my hunting I choose other calibers and heavier rounds.

As far as expansion at subsonic speeds, I think you will find the answer is "no." When you start a round at 2700 to 3000 feet per second it needs to hold together in such a way that it will not "expand" at subsonic speeds.

[Patent guy]

For this test I'll be sticking to magazine loaded ammo, this means 77gr SMK's loaded to 2.250 COAL. I'll be starting with Varget as a propellant since I have load data for that, but I'll also be testing RE15, BLC(2), and TAC in a search for higher velocities.
Terminal Ballistics Test
Once the maximum practical range of a load is determined the terminal ballistics at that range will be tested. Using 10% Knox gelatin covered in a layer of denim, the round must penetrate at least 13" to be considered effective. If the round fails to penetrate 13" the test will be repeated. If it fails a second time the range will be reduced 100 yards and the test conducted again until adequate penetration is achieved.

[/quote]

Excellent thread!  I'm unclear on the purpose, though.  If you want to identify the best long range load for your rifle, are you defining "best" in terms of external (in flight) ballistics or terminal (in meat) ballistics?  My reason for suggesting this choice early is that SMK's are not designed to "penetrate" anything.  Even if we assume that the 77gr "OTM" military rounds (like Black Hill's 5.56 77gr OTM) are the same, those terminal ballistics are evaluated differently (not just penetration depth).  Barnes has "TSX" and other projectiles which are designed to penetrate and expand, but also provide excellent external ballistics (with high BC and sectional density).  By the way, I have just chronographed some Black Hill's 5.56 77gr OTM which showed pressure signs in two of my ARs and in a 20"bbl, I measured an average velocity of 2850fps.

[AlaskaRed]

I'm trying to determine two things. How far out can I maintain accuracy with the round, and how much juice does it have at that range. It's my understanding that the FBI uses 13" of penetration in 10% ballistics gel as a minimum performance for handgun ammo so i figured that would be a reasonable metric.

[Patent guy]

http://www.shootingtimes.com/2012/03/21/special-forces-to-civilians-black-hills-mk-262-mod-1-review/

Here is something about the development thinking for the 77gr ammo developed by BH to accomplish similar objectives.  The BH ammo I tested came in the same red box shown in this article, and in my shooting/testing showed signs of excess pressure (ejector smears and popped primers).  Based on this article, testing was done at 1000yds.  There is a description of the wound channel creation mechanism and I'd bet you can find the actual DoD report which details these results in unclassified literature.  Reports like these might help steer you in your development work. 

[AlaskaRed]

I performed 3 ladder tests with RE15, TAC, and BLC(2). What I learned is that 100 yards is far, far too close to conduct a ladder test. I intended to do 300 yards, but changed it because I would have had to fire one shot, walk down range, mark the hole and walk back. With 54 rounds to fire and 1 half hour in between cease fires it would have taken me far too long to conduct the test.

Since then I've been informed of a technique that will allow me to conduct the ladder test much more quickly. Using multi colored sharpie markers I can color the tip of the bullet and the color will imprint itself on the paper when the bullet passes through. If you want more info on this, here is a wonderful article on 6mmbr[2] (6mmbr and accurateshooter are amazing websites for those of you interested in precision).

But there is good news as well, last weekend I got a chance to do some shooting at the relatively close 1000 yard range using my old standby load of a 77gr SMK in front of 24.0gr of varget. This range is very new, just opened a few months ago, and there is a slight depression between 700 and 1000 which along with the tall grass made it impossible to get LoS on the 800 or 900yard targets. However we got good data on the 700 yard line and the rifle is perfectly capable of conducting a test on ballistics gel at that range. Here's the photo of the 700 yard steel target [3] . The 3 circled shots are my hits, the one above it are from a .308. For scale the target is 18 3/4 inch tall and 20" wide.

http://i.imgur.com/kmBb7nV.png?2

Time for a brief interlude to rant: People who cherry pick groups to misrepresent the accuracy of their rifle annoy the hell out of me. My rifle is NOT a 0.5 MOA gun. Yes it will on occasion produce some really good groups, but luck and random chance play a big role in 3 and 5 round groups. If you want to say your rifle is 0.X MOA you'd better be prepared to demonstrate it with at least a 20 round group, and no throwing out flyers to make the rifle look good.

Anyways this is how I'll be proceeding from here on out. I'll be doing a ballistics test with at least 2, hopefully 3 types of ammo. I am going to shoot at 10% knox gelatin covered in denim at 700 yards with my varget load, my TAC load and if I can find it some mk262 ammo.

[fisherdawg]

I performed 3 ladder tests with RE15, TAC, and BLC(2). What I learned is that 100 yards is far, far too close to conduct a ladder test. I intended to do 300 yards, but changed it because I would have had to fire one shot, walk down range, mark the hole and walk back. With 54 rounds to fire and 1 half hour in between cease fires it would have taken me far too long to conduct the test.

Since then I've been informed of a technique that will allow me to conduct the ladder test much more quickly. Using multi colored sharpie markers I can color the tip of the bullet and the color will imprint itself on the paper when the bullet passes through. If you want more info on this, here is a wonderful article on 6mmbr[2] (6mmbr and accurateshooter are amazing websites for those of you interested in precision).

But there is good news as well, last weekend I got a chance to do some shooting at the relatively close 1000 yard range using my old standby load of a 77gr SMK in front of 24.0gr of varget. This range is very new, just opened a few months ago, and there is a slight depression between 700 and 1000 which along with the tall grass made it impossible to get LoS on the 800 or 900yard targets. However we got good data on the 700 yard line and the rifle is perfectly capable of conducting a test on ballistics gel at that range. Here's the photo of the 700 yard steel target [3] . The 3 circled shots are my hits, the one above it are from a .308. For scale the target is 18 3/4 inch tall and 20" wide.

Time for a brief interlude to rant: People who cherry pick groups to misrepresent the accuracy of their rifle annoy the hell out of me. My rifle is NOT a 0.5 MOA gun. Yes it will on occasion produce some really good groups, but luck and random chance play a big role in 3 and 5 round groups. If you want to say your rifle is 0.X MOA you'd better be prepared to demonstrate it with at least a 20 round group, and no throwing out flyers to make the rifle look good.

Anyways this is how I'll be proceeding from here on out. I'll be doing a ballistics test with at least 2, hopefully 3 types of ammo. I am going to shoot at 10% knox gelatin covered in denim at 700 yards with my varget load, my TAC load and if I can find it some mk262 ammo.

I saw that group on steel last night when I picked up the kit from Eric. Impressive.
Tell me more about the LoS issues at 800 & 900 -- anyway to address it with somewhat taller stands? Say the legs were 8' instead of the current 5'?

[AlaskaRed]

It was tough to see the cross beams on the 800&900 yard target. 8ft might do it, but 10 would be safer. It might be worth while to build a couple of extra tall frames and just leave them at USSA.

[fisherdawg]

It was tough to see the cross beams on the 800&900 yard target. 8ft might do it, but 10 would be safer. It might be worth while to build a couple of extra tall frames and just leave them at USSA.

We'll need a step ladder to erect it at 10'.  I bet if we ask nice USSA they'll let us store 2 10' stands & 6' step ladder up there somewhere secure. I'll start watching Craigslist / Alaska's list for a cheap ladder.

[Charles McKinley]

Can you make the stand hindge so you can lower it to change/mark targets?  It would sure beat lugging a ladder out there and trying to find a level enough spot to get up it safely.

[fisherdawg]

Can you make the stand hindge so you can lower it to change/mark targets?  It would sure beat lugging a ladder out there and trying to find a level enough spot to get up it safely.

Yeah, I think that's a good idea!